Temperature and aging effects on ultimate bearing strength and fatigue of polymeric composite joints

The ultimate bearing strength (UBS) and fatigue performance of IM7/PETI-5 composite materials in a quasi-isotropic lay-up, 64 plies thick was determined using a compressive bearing test set-up. Strength testing was performed at room temperature, 177°C (350 F) and –50°C (-58 F). Fatigue tests were performed at 177°C (350 F). Some specimens were thermally aged at 177°C (350 F) for up to 10,000 hours. It was found that the IM7/PETI-5 composite material‘s UBS and fatigue performance was essentially unaffected by the thermal aging. The elevated temperature tests resulted in a lower UBS and the cold temperature tests resulted in a slightly higher UBS. However, the cold temperature bearing failure was quite dramatic, resulting in widespread delamination due to the brittleness of the matrix.